Transmission Clutch Fill During Start-Stop
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Solution Overview
Problem
Automatic transmissions experience hesitation during engine start-stop operations due to the loss of hydraulic pressure, requiring costly electric pumps and additional logic, valves, and sensors to quickly re-engage the clutch for first gear.
Innovation Solution
A friction element engagement system with a piston housed in a chamber, divided by a controller arm, utilizing fluid pressure from a pump to engage and disengage clutches without the need for additional electric pumps, logic, or sensors, by using a limit valve to maintain pressure and vent fluid when the engine is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an electric pump is used to maintain hydraulic pressure during start-stop operation, then clutch engagement speed is improved, but device complexity and cost increase
Solution Approach 1:
The piston is pre-positioned in the engaged state before engine start, with fluid already pressurized in the second chamber. When the engine restarts, the clutch is already engaged and ready to transmit torque immediately, eliminating the need for electric pumps and additional control systems.
Solution Approach 2:
The system uses the engine's own hydraulic pump to automatically re-pressurize the second chamber when the engine restarts, eliminating the need for external electric pumps. The limit valve automatically regulates pressure without additional sensors or control logic.
2Loss of time
If hydraulic pressure is maintained in the transmission during start-stop operation, then clutch engagement time is reduced, but energy consumption increases
Solution Approach 1:
Hydraulic pressure is maintained in the second chamber only when needed (during start-stop operation), not continuously. The piston remains in the engaged position with pressure already present, so when the engine restarts, no additional energy is required to engage the clutch.
Solution Approach 2:
The hydraulic pump operates periodically only during engine restart events rather than continuously, reducing energy consumption. The limit valve automatically manages pressure cycles without requiring continuous power input.
3Ease of manufacture
If a limit valve is used to control fluid pressure in the first chamber, then manufacturing cost is reduced, but pressure control precision may be affected
Solution Approach 1:
The limit valve provides sufficient pressure control precision for the specific function of maintaining clutch engagement, without requiring high-precision control throughout the entire hydraulic system. The valve is tuned to the specific pressure range needed for clutch operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables quick engagement of transmission clutches during start-stop operations without hesitation, eliminating the need for additional components and reducing fuel consumption by maintaining clutch pressure when the engine restarts.
Implementation Method 1
a fluid supply apparatus for supplying fluid to the first and second chambers, wherein a position of the piston may be determined by a pressure of the fluid in the first chamber and a pressure of the fluid in the second chamber
Implementation Method 2
The first valve may be a limit valve that limits the pressure of the fluid in the first chamber. The first valve may limit the fluid pressure in the first chamber to between ten to fifteen pounds per square inch.
Data Source
AI summary
An apparatus and a method for engaging a friction element, e.g., a clutch, in an automatic transmission. The apparatus includes a piston contained within a housing that is used to apply pressure to and operate the friction element. The piston divides the housing into first and second chambers that are supplied with fluid by various valves. The pressure of the fluid in the chambers controls the position of the piston.